Role of Estrogen Receptor Variants in Tumorgenesis of Human Breast Cancer

In order to determine whether differences exist in expression of estrogen receptor ER variant mRNAs between normal and tumor breast tissues, we have analyzed by reverse transcription-polymerase chain reaction RT-PCR ER variants mRNA expression in matched normal breast tissue and breast tumor components from 11 different patients. We have set up two assays Triple-Primer-PCR and long-range PCR that allow the quantitative evaluation of clone 4 ER variant and exon-deleted ER variant mRNAs expression within each samples. A general trend toward a higher expression of exon 5-deleted, exon 7-deleted ER variant and clone 4 estrogen receptor ER variant in the tumor component compared to the normal counterpart of matched samples has been seen. This is consistent with previous observations made on independent samples. The number of cases together with the amount of starting material frozen tissue sections per samples needs to be increased in order to establish confidently any statistically significant differences. The relative spatial localization of normal and tumor components together with the phenotypic characteristics of the tumors ER and progesterone receptor values, as measured by ligand binding assay are two parameters that will be taken into account in the selection of additional cases.